Configuring a shared library to accommodate relocatable data in a pervasive device

ABSTRACT

A method, system, architecture and apparatus for generating a shared library for a pervasive device target platform which can accommodate relocatable data. A tool chain in furtherance of this purpose can be arranged in accordance with the present invention to include a compiler programmed to compile source code into a compiled object and a linker programmed to link the compiled object into a linked object using a relocatable data segment. In this regard, in a preferred aspect of the invention a linker configuration file can be included for use in the linker which specifies the use of the relocatable data segment in lieu of a position independent data segment. The tool chain further can be arranged to include a relocation data extraction tool programmed to extract relocation data from the linked object and to dispose the relocation data in a relocation data file configured for disposition in a pervasive device.

BACKGROUND OF THE INVENTION

1. Statement of the Technical Field

The present invention relates to pervasive device applicationsdevelopment and more particularly to configuring a shared library fordeployment in a pervasive device.

2. Description of the Related Art

Computing has changed dramatically since the advent of the personalcomputer in the latter part of the twentieth century. Whilst the vastmajority of end user applications operated within the single threaded,single tasking desktop computing environment, modern end userapplications operate in a variety of disparate environments. In thisregard, the modern computing environment can range from multi-threadedmulti-tasking operating desktop computing system, to equivalentlyadvanced pervasive computing devices, including handheld personaldigital assistants, cellular telephones, paging devices and the like. Tosupport the rapid growth of the pervasive device market, manyapplications developed for the desktop computing environment have beenported to the pervasive device computing environment.

Regardless of the computing environment, producing an end userapplication typically involves the generation of computing source codeconforming to a specific computing language specification, followed by acompilation step. The compilation step can produce one or more binaryobjects suitable for linkage and assembly into an executableapplication. In this regard, tool chains are widely available in themarketplace which can manage the application generation process.Notably, in the course of developing an executable application, one ormore shared libraries can be referenced and relied upon for incorporatedlogic, resources, or both so that the executable application itselfneedn't incorporate the referenced logic and resources. To that end,shared libraries can be produced in a similar fashion, though start upcode need not be included in a shared library as it must in anexecutable module.

Shared libraries which have been generated for the pervasive devicetarget platform typically are required to include position independentdata and code segments. Position independent data and code segmentsgenerally refer to program code and corresponding data which can executefrom different locations in memory and are usually associated with oldercomputing environments which lack a memory management unit. In referenceto shared libraries, the same library code and data can be mapped to alocation in each referencing application using a virtual memory systemwhere it will not overlap the application or other shared libraries.

Relocatable data and code segments, unlike position independent data andcode segments, are data and code segments whose memory location can bedetermined at link time or at run time in reference to a base address.In the simplest model of relocation, the loader performs the finalbinding of code to specific memory locations, and as it does so, itadjusts or relocates all of the pointers from one part of the loadedprogram to another. Relocation involves adding a constant, therelocation base, to each address which refers to another location in thesame program. The relocation base is usually the same as the address atwhich the first byte of the program is loaded.

Importantly, to enforce the requirement that shared libraries supportposition independent data and code segments, the compilation and linkagetools in the tool chains for pervasive device target platforms sometimesdo not support relocations to either of the data or text segment. Yet,many well-known programming standards, including the ISO C standard,require compliant tool chains to support relocations in the datasegment. As such, a multitude of existing applications developed for thedesktop environment cannot easily be ported to the pervasive deviceenvironment.

SUMMARY OF THE INVENTION

The present invention addresses the deficiencies of the art in respectto supporting relocatable data in a shared library and provides a noveland non-obvious method, system, architecture and apparatus forgenerating a shared library for a pervasive device target platform whichcan accommodate relocatable data. A method for configuring a sharedlibrary to accommodate relocatable data in a pervasive target device caninclude the step of modifying a main entry point in shared librarysource code to initialize data for the shared library using relocationinformation disposed in an associated shared library database resource.The modifying step can include inserting program code into the mainentry point for causing the shared library to trap a launch codeassociated with initializing the shared library for use. The modifyingstep also can include further inserting program code into the main entrypoint for handling the trapped launch code by initializing the data forthe shared library using the relocation information disposed in anassociated shared library database resource.

Once modified, the shared library source code can be compiled to producea compiled shared library object. Subsequently, the compiled sharedlibrary object can be linked to produce the shared library. In thisregard, the linking of the shared library can be specified to userelocatable data and code segments in lieu of position independent dataand code segments. For example, a scatter loading file can be retrievedand modified to indicate linkage using a relocatable data segment.Consequently, relocation information can be included in the linkedobject. As such, subsequent to linking, the relocation information canbe extracted from the compiled shared library object and once extracted,the relocation information can be persisted in the associated sharedlibrary database resource.

A tool chain can be arranged in accordance with the present invention toinclude a compiler programmed to compile source code into a compiledobject and a linker programmed to link the compiled object into a linkedobject using a relocatable data segment. In this regard, in a preferredaspect of the invention a linker configuration file, occasionallyreferred to as a scatter loading file, can be included for use in thelinker which specifies the use of the relocatable data segment in lieuof a position independent data segment. The tool chain further can bearranged to include a relocation data extraction tool programmed toextract relocation data from the linked object and to dispose therelocation data in a relocation data file configured for disposition ina pervasive device.

Additional aspects of the invention will be set forth in part in thedescription which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The aspectsof the invention will be realized and attained by means of the elementsand combinations particularly pointed out in the appended claims. It isto be understood that both the foregoing general description and thefollowing detailed description are exemplary and explanatory only andare not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute partof this specification, illustrate embodiments of the invention andtogether with the description, serve to explain the principles of theinvention. The embodiments illustrated herein are presently preferred,it being understood, however, that the invention is not limited to theprecise arrangements and instrumentalities shown, wherein:

FIG. 1 is a schematic illustration of a system configured to generate ashared library configured to accommodate relocatable data when deployedin a pervasive device target platform; and,

FIG. 2 is a flow chart illustrating a process for generating a sharedlibrary configured to accommodate relocatable data when deployed in apervasive device target platform.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is a method, system and apparatus for configuringa shared library to accommodate relocatable data in a target pervasivedevice. In accordance with the present invention, a tool chain forproducing applications for a target pervasive device can be configuredto place the data for an application in a relocatable segment in lieu ofplacing the data in a position independent segment. Subsequently, thesource code for the application can be compiled and linked. Therelocation information produced by the linker can be extracted from thelinked object and stored in a form suitable for access in the targetpervasive device. In this way, upon initializing the data for theapplication during the execution of the application, the application canaccess the data according to the relocation information stored in thetarget pervasive device.

In further illustration of the principles of the present invention, FIG.1 is a schematic illustration of a system configured to generate ashared library configured to accommodate relocatable data when deployedin a pervasive device target platform. The system can include a toolchain including at least a compiler 115 and a linker 125. The compiler115 can be programmed to process source code 105 into a compiled object120. The linker 125, in turn, can be programmed to process the compiledobject 120 into a linked object 135. Finally, in accordance with thepresent invention, a relocation data extraction tool 145 and a linkeddata extraction tool 140 can be included in the tool chain.

The relocation data extraction tool 145 can be configured to extractrelocation information from the linked object 135. The relocation dataextraction tool 145 further can be configured to store the extractedrelocation information in a relocation database file 150 configured fordisposition in a target pervasive device. The linked data extractiontool 145, by comparison, can be configured to extract applicationresource data from the linked object 135. Subsequently, the linked dataextraction tool 145 can store the extracted application resource data ina resource database file 155 configured for disposition in a targetpervasive device. Finally, both the relocation database file 150 and theresource database file 155 can be merged into a single shared librarydatabase 165 through the operation of a database merge tool 160 includedin the tool chain.

Notably, the source code 105 of the application can be modified toincorporate configuration code 110. The configuration code 110 caninclude logic for trapping an initialization event and configuring theaddressability of application data according to the relocationinformation stored in the shared library database 165. In addition tothe source code 105, the linker configuration file 130 associated withthe linker 125 also can be modified to cause the linkage of theapplication data and code in a relocatable manner rather than a positionindependent manner as would be the case otherwise in a target pervasivedevice. In this way, the relocation data extraction tool 145 can extractthe relocation information from the linked object 135 produced inconsequence of the modified linker configuration file 130.

To further explain the operation of the tool chain of the presentinvention, FIG. 2 is a flow chart illustrating a process for generatinga shared library configured to accommodate relocatable data whendeployed in a pervasive device target platform. Beginning in block 210,the main entry point of the shared library source code can be modifiedto trap an initialization event. For example, in a handheld device, thelaunch code associated with application initialization can be trappedwithin a case statement and the initialization event can be handled withlogic for retrieving the relocation information for the application froma database resource associated with the application. Once configurationlogic has been added to the main entry point of the application, inblock 220 the shared library source code for the application can becompiled.

In block 230, the object code produced by the compilation step of block220 can be linked to place application data and code in respectiverelocatable data and code (text) segments. Notably, the linking canutilize the relocatable data and code segments in lieu of the defaultposition independent data and code segments. In a preferred aspect ofthe invention, the utilization of the relocatable data and codesegements can be specified by modifying a linker configuration file forthe linker. Subsequently to the linking step, in blocks 240A and 240B,the relocation data and resource data produced by the linker can beextracted separately and temporarily stored before both are merged inblock 250 into a single database resource for the shared library.

In block 260, the application can be executed, in consequence of whichthe configuration code can be executed according to the modified entrypoint. Through operation of the modified entry point, the relocationinformation can be retrieved from the database resource and utilized toproperly initialize the application data. In this way, relocatable datacan be supported within the pervasive device, despite the inherentsupport only for position independent data. As a natural consequence ofthe present invention, then, applications initially developed for thedesktop environment which supports relocatable data segments can be moreeasily ported to the pervasive device environment.

The present invention can be realized in software. An implementation ofthe method and system of the present invention can be realized in acentralized fashion in one computer system, or in a distributed fashionwhere different elements are spread across several interconnectedcomputer systems. Any kind of computer system, or other apparatusadapted for carrying out the methods described herein, is suited toperform the functions described herein.

A typical combination of hardware and software could be a generalpurpose computer system with a computer program that, when being loadedand executed, controls the computer system such that it carries out themethods described herein. The present invention can also be embedded ina computer program product, which comprises all the features enablingthe implementation of the methods described herein, and which, whenloaded in a computer system is able to carry out these methods.

Computer program or application in the present context means anyexpression, in any language, code or notation, of a set of instructionsintended to cause a system having an information processing capabilityto perform a particular function either directly or after either or bothof the following a) conversion to another language, code or notation; b)reproduction in a different material form. Significantly, this inventioncan be embodied in other specific forms without departing from thespirit or essential attributes thereof, and accordingly, referenceshould be had to the following claims, rather than to the foregoingspecification, as indicating the scope of the invention.

1. A method for configuring a shared library to accommodate relocatabledata in a pervasive target device, the method comprising the steps of:modifying a main entry point in shared library source code to initializedata for the shared library using relocation information disposed in anassociated shared library database resource; specifying linking of theshared library using relocatable data and code segments in lieu ofposition independent data and code segments; compiling said sharedlibrary source code to produce a compiled shared library object andlinking said compiled shared library object to produce the sharedlibrary; extracting relocation information from said compiled sharedlibrary object; persisting said extracted relocation information in saidassociated shared library database resource; wherein said specifyingstep comprises the steps of: retrieving a linker configuration file;and, modifying said retrieved linker configuration file to indicatelinkage using a relocatable data segment.
 2. The method of claim 1,wherein said modifying step comprises the steps of: inserting programcode into said main entry point for causing the shared library to trap alaunch code associated with initializing the shared library for use;further inserting program code into said main entry point for handlingsaid trapped launch code by initializing said data for the sharedlibrary using said relocation information disposed in said associatedshared library database resource.
 3. The method of claim 1, wherein saidmodifying step comprises the step of modifying said retrieved linkerconfiguration file to indicate linkage using a relocatable data segmentin lieu of using a position independent data segment.
 4. The method ofclaim 1, further comprising the steps of: extracting resource data fromsaid compiled shared library object; and, persisting said resource datawith said extracted relocation information in said associated sharedlibrary database resource.
 5. The method of claim 4, wherein saidpersisting step comprises the step of merging a database file containingsaid extracted resource data and a database file containing saidextracted relocation information into said associated shared librarydatabase resource.
 6. The method of claim 1, further comprising the stepof installing said shared library object and said associated sharedlibrary database resource in a pervasive device.